Adult cannot welcome what may be seen around ancient capital (7)
I believe the answer is:
'may be seen around ancient capital' is the definition.
I can't tell whether this defines the answer.
'adult cannot welcome' is the wordplay.
'adult' becomes 'a' (abbreviation).
'cannot' becomes 'can't' (contraction).
'welcome' becomes 'hi' (both are greetings).
'what' is the link.
Can you help me to learn more?
(Other definitions for acanthi that I've seen before include "Prickly plants" , "bloomers" .)